First published by IBM at: http://www-106.ibm.com/developerworks/linux/library/l-powhist/
All rights retained by IBM and the author.

In the beginning, each computer's central processing unit, or CPU, was unique. Each had its own instruction set, which was incompatible with any other. All of that changed back in the thermionic valve (or "vacuum tube") days with the introduction of the IBM S/360^TM line of computers, in 1964. Suddenly, code didn't have to be thrown away and reimplemented every time you bought a new computer. Today's IBM mainframes still maintain backwards-compatibility with that revolutionary 1962 instruction set. And the same spirit of compatibility infuses IBM's other CPU lines.

At the user-mode level, the instruction set of the PowerPC^® family of processors provides full application compatibility, from the lowliest automated traffic light to the powerful Apple Xserve G5. In addition, PowerPC microprocessors share a large common instruction set with IBM's other RISC processor lines, POWER^TM and Star, which leads to "near" compatibility across all three families. In many cases, this equals binary compatibility; in some cases, it means that a simple recompilation is needed; in all cases, it means that porting is a breeze.

IBM's four families of processors—the POWER architecture, the PowerPC family of processors, the Star chips, and even the line of chips that power IBM mainframes—all have a common ancestor: the IBM 801.

Family inheritance
The IBM 801 started out attempting to solve the same problem as a lot of the computers in the 1970s: switching telephone calls. The design team's goal was to complete one instruction per clock cycle, and to accommodate 300 calls per minute.

Most of the computers of the day, such as the IBM S/360 mainframe, had complex and redundant (or "orthogonal") instruction sets known today as CISC (complex instruction set computer). The trend towards miniaturization in computing, which began with the 1947 invention of the transfer resistor (or "transistor") only exacerbated this. As integrated circuits grew smaller, designers took advantage of the extra space to cram even more instructions into the chip. All of this complexity meant that by the 1970s, computer chips could do really amazing things (like power increasingly complex digital watches). But it also meant that the chips needed more machine time to execute, making it impossible for the 801 team to achieve their performance goals.

IBM's John Cocke was no stranger to the battle against complexity. He had already worked on the IBM Stretch computer, a rival to the IBM 704 mainframe, and on Stretch successor ACS (Advanced Computing Systems), rival to the 704's successor, the S/360.

Compatible by design The PowerPC architecture is organized into three instruction-set levels called "books." Book I is the base set of user instructions and registers that should be common to all PowerPC implementations. Book II defines additional user-level functionality that is outside the normal requirements for application software. Book III defines privileged operations typically required by operating systems. For a detailed outline of the PowerPC architecture and what it means for programmers, read "A developer's guide to the PowerPC architecture."

He sliced away at the redundancy in the instruction set and designed a machine with half the circuits of its contemporaries—that ran twice as fast as they did. The fast core and fewer circuits led not only to greater performance, but also to lower power consumption and -- perhaps most important for many consumers today—much lower costs. This architecture became known as RISC (reduced instruction set computer). Some prefer to call it "load-store," pointing out that the instruction set of a RISC computer can number as many as 100 instructions or more (as the POWER architecture does). Others counter that the RISC is not a reduced set of instructions, but rather a set of reduced instructions—each of the complex instructions of the CISC is broken down into shorter basic building blocks that can then be combined.

In any case, the complexity that was removed from the CPU didn't just disappear; it was pawned off on the compiler. In order to do that gracefully, John Cocke became not only an expert in compilers, but especially in optimizing them. His work on RISC and optimizing compilers won him many awards, not the least of which was the 1987 Turing Award.

As for the IBM 801, it never did become a telephone switcher. Instead, it became the first RISC chip and powered many IBM hardware products—for a time, it even did a stint as a minicontroller and processor in its rival, the IBM mainframe series.

The RISC architecture soon came to dominate the workstation and embedded markets, and John Cocke moved on to other projects. In the 1980s, he had a chance to refine his 801 design in a project that was code-named "America" and that would become the POWER series of chips. He even had a hand in the development of the PowerPC architecture a few years later. Like the 801, the PowerPC was designed to be a universal microprocessor that could run on any machine, from the smallest to the tallest.

Today, the RISC architecture is the single most common CPU type in use and is the basis for everything from workstations to cell phones, video game consoles to supercomputers, traffic lights to desktops, and broadband modems to automobile fuel-injection and collision avoidance systems. Even x86 chip manufacturers, which continued for quite a time to produce CISC chips, have based their 5th- and 6th-generation chips on RISC architectures and translate x86 opcodes into RISC operations to make them backwards-compatible.

POWER
POWER stands for Power Optimization With Enhanced RISC and is the main processor in many IBM servers, workstations, and supercomputers. Descended directly from the 801 CPU, it is a 2nd-generation RISC processor. Introduced in 1990 to power the RS, or RISC System/6000 UNIX workstations (now called the eServer^TM pSeries^®), POWER exists in iterations from POWER1, POWER2^TM, POWER3^TM, and the current top end, POWER4^TM. The POWER4 processor is the pinnacle of single-chip performance today.

The 801 was a very simple design. But because all instructions completed in one clock cycle, it lacked floating-point and superscalar (parallel processing) ability. The POWER architecture set out to correct this—some would say, perhaps, to overcorrect it. With more than 100 instructions, the POWER is a pretty complex RISC.

Highlights for each iteration follow; for comprehensive details, please see the links listed in Resources.

• POWER1
  Released in 1990: 800,000 transistors per chip
  Unlike other RISC processors of the day, POWER1 was functionally partitioned. This gave it superscalar abilities beyond those of mortal chips. It also had separate floating-point registers and could scale from the low to the high end of the UNIX workstations it was built for. The very first POWER1 was actually several chips on a single motherboard; this was soon refined down to one RSC (RISC Single Chip) with more than a million transistors. The RSC implementation of the POWER1 microprocessor was used as the central processor for the Mars Pathfinder mission and is the chip from which the PowerPC line is descended.
• POWER2
  Released in 1993 and in use until 1998: 15 million transistors per chip
  The POWER2 added a second floating-point unit (FPU) and more cache. The PSSC superchip, a single-chip implementation of the POWER2's eight-chip architecture, powered the 32-node IBM DEEP BLUE^® supercomputer that beat world champion Garry Kasparov at chess in 1997.
• POWER3
  Released in 1998: 15 million transistors per chip
  The first 64-bit symmetric multiprocessor (SMP), POWER3 is completely compatible with the original POWER instruction set—and compatible with the PowerPC instruction set as well. The POWER3 was designed for work on scientific and technical computing applications from aerospace and pharma to weather prediction. It features a data prefetch engine, non-blocking interleaved data cache, dual floating point execution units, and many other goodies. The POWER3-II reimplemented POWER3 using copper interconnects, delivering double the performance at about the same price.
• POWER4
  Released in 2001: 174 million transistors per processor
  A gigaprocessor incorporating 0.18-micron copper and SOI (Silicon-on-Insulator) technology, the POWER4 is the single most powerful chip on the market today. It inherited all of the characteristics of the POWER3—including compatibility with the PowerPC instruction set—but reinvented itself with a completely new design. Each processor has two 64-bit 1Ghz+ PowerPC cores, making it the first server processor with a multicore design on a single die (also known as "SMP on a chip," or "system on a chip"). Each processor can execute as many as 200 instructions simultaneously. The POWER4 supersedes the Star family of processors and is the power behind the IBM Regatta servers as well as being the father of the PowerPC 970 processor (also known as the Apple G5). The POWER4+^TM (also known as POWER4-II) does the same, but at higher frequencies and with less power consumption.
• POWER5^TM
  Due out in 2004
  Like the POWER3 and POWER4, the POWER5 unifies the POWER and PowerPC architectures. It will feature communications acceleration, chip multiprocessing, and simultaneous multithreading (SMT). Recent internal testing shows that POWER5-based eServer systems are expected to offer four times the performance of the first POWER4-based servers. It will make its appearance in a new line of servers that are code-named "Squadrons" and in the teraflop ASCI Purple computer scheduled to be delivered to Lawrence Livermore in the second half of 2004.
• POWER6^TM
  Under wraps.

Star power
RS64 chips first appeared in 1998 and are known within IBM as the Star family, because most of the code words for the various iterations contained the word "star" or something like it (the notable exception is the original RS64, code-named "Apache").

Descended from a modified PowerPC architecture, they also inherited a number of traits from the POWER line. From inception they were optimized for one thing only: commercial workloads. This degree of specialization put them at the top of the UNIX server game for nearly a decade.

The RS64 family leaves things like branch prediction, exceptional floating-point powers, and hardware prefetch to its POWER3 cousin and focuses instead on exceptional integer performance and large, sophisticated on- and off-chip caches. The RS64 family has been 64-bit for its entire span, and introduced multithreading in the RS64 IV iteration in 2000. The RS64 can scale to as many as 24 processor SMP in a single machine, and—unlike its POWERful cousins—consumes as few as 15 watts per processor.

These qualities make it ideal for things like on-line transaction processing (OLTP), business intelligence, enterprise resource planning (ERP), and other large and hyphenated, function-rich, database-enabled, multi-user, multi-tasking jobs with high cache miss rates—including Web serving. RS64 chips shipped in the IBM eServer iSeries^TM (RS series) and pSeries (AS series) only.

• RS64
  Released in 1997, code name: Apache
  The first RS64 and the world's first 64-bit PowerPC RISC. Both superscalar and scalable, it was more compatible with POWER1 than later RS64 chips would be. By focusing on commercial workloads, it was able to implement functions on one chip that had previously required seven. It was used in the AS/400^® (then called A35) and RS/6000^®.
• RS64 II
  Released in 1998, code name: Northstar
  The second iteration featured four processors per card and up to three cards per RS/6000 to create a 4-way, 8-way, or 12-way SMP system.
• RS64 III
  Released in 1999, code name: Pulsar
  The first RS64 to use IBM copper and SOI (Silicon on Insulator), now with six processor cards scaling up to 24-way SMP.
• RS64 IV
  Released in 2001, code names: IStar, SStar
  The first mass-market processor to implement multithreading, RS64 IV was faster and smaller than its predecessors.

Today, the convergence of commercial and scientific computing has created a need for a single processor to address both markets. Thus the Star family is being succeeded by the redesigned POWER4.

PowerPC
The PC in PowerPC stands for performance computing. Descended from the POWER architecture, it was introduced in 1993. Like the IBM 801, it was designed from the beginning to run on a broad range of machines, from battery-operated handhelds to supercomputers and mainframes. But it saw its first commercial use on the desktop, in the Power Macintosh 6100.

Born of an alliance between Apple, IBM, and Motorola (also known as the AIM alliance), the PowerPC was based on POWER, but with a number of differences. For instance, PowerPC is open-endian, supporting both big-endian and little-endian memory models, where POWER had been big-endian. The original PowerPC design also focused on floating-point performance and multiprocessing capabilities. Still, it did and still does include most of the POWER instructions. Many applications work on both, perhaps with a recompile to make the transition.

While IBM and Motorola develop their chips separately, at the user level, all PowerPC processors run the same core PowerPC instruction set, ensuring full ABI compatibility for the software products that run on them. Since 2000, Motorola and IBM PowerPC chips have followed the Book E spec, which provides additional enhancements to make PowerPC more attractive for embedded processor applications such as networking and storage equipment as well as for consumer devices.

Aside from compatibility, one of the best things about the PowerPC architecture is that it is open: it specifies an instruction set architecture (ISA) that allows anyone to design and fabricate PowerPC-compatible processors; and source code for software modules developed in support of PowerPC is freely available. Finally, the small size of the PowerPC core leaves a great deal of room on each die for additional components, from added cache to coprocessors, allowing for an amazing amount of design flexibility.

Two of IBM's four server lines are based on the PowerPC architecture as are the Apple Computer desktop and server lines, the Nintendo GameCube, and the IBM Blue Gene^® supercomputer.

Today, the three main PowerPC families are the embedded PowerPC 400 series and the stand-alone PowerPC 700 and PowerPC 900 families. For historical perspective, we will also give highlights for the stand-alone PowerPC 600, because it was the first.

• PowerPC 600 family
  The PowerPC 601 was the first chip in the first PowerPC family. A sort of bridge between the POWER and PowerPC architectures, it maintained more compatibility with POWER1 than later PowerPCs (even those from the same family), as well as compatibility with the Motorola 88110 bus. The PowerPC 601 made its debut in the very first PowerMac 6100 in 1994, running at blazing speeds of up to 66 MHz. The next chip in the line was the 603, a low-end, low-power core that is the chip most often found in cars. Released at the same time as the PowerPC 603^®, in its day the PowerPC 604^® was the most powerful high-volume chip in the industry. Both the 603 and 604 were rereleased in tweaked "e" versions (the 603e and 604e) with improved performance. Finally, the first 64-bit PowerPC, the very high-end PowerPC 620^®, was released in 1995.
• PowerPC 700 family
  With a debut in 1998, the PowerPC 740 and PowerPC 750 were very similar to the 604e—some people would say they are all members of the same 600/700 family. The PowerPC 750 was the world's first copper-based microprocessor, and when used in Apple computers is usually known as the G3. It was rather quickly eclipsed by the G4, or Motorola 7400. The 32-bit PowerPC 750FX wowed the industry with speeds of up to 1 GHz when it was released in 2002. IBM followed this in 2003 with the 750GX, which incorporates 1MB of L2 cache at speeds of 1GHz at around seven watts of power consumption.
• PowerPC 900 family
  The 64-bit PowerPC 970, a single-core version of the POWER4, can process 200 instructions at once at speeds of up to 2 GHz and beyond—all while consuming just tens of watts of power. Its low power consumption makes it a favorite with notebooks and other portable applications on the one hand, and with large server and storage farms on the other. Its 64-bit capability and single instruction multiple data (SIMD) unit accelerate computationally intensive workloads such as multimedia and graphics. It is used in Apple desktops, Apple Xserve servers, imaging applications, and—increasingly—in networking applications. The Apple Xserve G5 features the first use of the new PowerPC 970FX—the first chip made using both strained silicon and SOI technologies together, enabling the chip to run at even greater speeds with even less power consumption.
• PowerPC 400
  This is the embedded family of PowerPC processors. The PowerPC's flexible architecture allows for a great deal of specialization, and that is nowhere so apparent as in the 400 family. It is found in applications ranging from set-top boxes to the IBM Blue Gene supercomputer. On one end of the spectrum, the PowerPC 405EP consumes just one watt of power to achieve speeds of up to 200 MHz, while the copper-based 800 Mhz PowerPC 440 series offer the industry's highest performance for an embedded processor. Each subfamily can be specialized as well; for instance, the PowerPC 440GX's dual Gigabit ethernet and TCP/IP off-load acceleration can decrease utilization for packet-intensive applications by more than 50 percent. A large array of products are built around highly modified PowerPC 400 family cores, not the least of which is the Blue Gene supercomputer with two PowerPC 440 processors and two FP (floating point) cores per chip. IBM recently announced a deal with Applied Micro Circuits Corp. for AMCC to buy intellectual property and assets associated with the PowerPC 400. IBM will continue to manufacture the products for AMCC and will continue to design and manufacture PowerPC 400 embedded cores in its ASIC and systems-on-a-chip offerings.

Originally thought of as a desktop chip, the PowerPC's low power needs make it an excellent candidate for the embedded space, and its high performance makes it attractive for advanced applications. It is well suited for everything from video game consoles and multimedia entertainment systems, to personal digital assistants and cell phones, to base stations and PBX switches. It is at home in broadband modems, hubs and routers, automotive subsystems, printers, copiers, and faxes. And of course, desktop systems too.

CMOS
You will remember that the 801 project was in great part a reaction to the complexity of CISC systems and specifically, the extreme CISC of the IBM mainframe. Nevertheless, IBM mainframes were also beneficiaries of the 801 project, and so are distantly related to IBM's three lines of RISC processors. IBM's "fourth family" of processors, the mainframe chips, have a very complicated family history of their own.

Breaking the speed limits of Moore's Law Everyone knows that IBM originated FORTRAN and disk drives; but did you know IBM is also one of the leading innovators in chip technology? Here is a quick rundown: Copper conductors The semiconductor industry has dreamed of using copper, which conducts electricity 40 percent more efficiently than aluminum, for ages. But it was only recently that a manufacturing process was discovered to accomplish this goal. Taking a page from Edison's notebook, IBM researchers use tungsten to create copper-based chips capable of running significantly faster than their aluminum-based brethren. Silicon-germanium (SiGe) Used in bipolar chipmaking in place of the more expensive gallium arsenide process, SiGe allows for significant improvements in operating frequency, current, noise, and power capabilities. Silicon on insulator (SOI) Placing a thin layer of insulation between the silicon surface and the transistors protects the transistors from "electrical effects," leading to higher performance and lower power consumption. Strained silicon This technique strains (or stretches) silicon, thus speeding the flow of electrons through a chip, increasing performance and lowering power consumption without any miniaturization. When coupled with SOI, the use of strained silicon speeds performance and decreases power consumption even more.

One of the reasons for this is that mainframes rely much less on the CPU and more on system architecture and I/O channels than other types of computers. The revolutionary S/360 family of mainframes that introduced compatibility to the industry were still powered by magnetic cores. With a name change to S/370^TM in 1971, they became the first mainframes in the industry to switch to chips. Of course they used CISC chips; specifically, bipolar junction transistors with a CISC architecture. A decade or so later, they briefly switched to a RISC architecture when it was discovered -- much to everyone's surprise—that it increased performance by a significant factor. But an even more significant change came when they began to use CMOS instead of bipolar transistors; the first generation (or G1) CMOS mainframe chips came out around 1985, and by 1997 IBM announced that henceforth all mainframes would ship only with CMOS and never again with bipolar transistors. And it isn't only mainframes that have made the switch to CMOS: while bipolar transistors ruled the early chipmaking world, most of the processors made today are CMOS.

So what are these CMOS chips, exactly? Well, CMOS (complementary metal-oxide semiconductor) chips use metal-oxide semiconductor field effect transistors (MOSFETs). These are fundamentally different from bipolar transistors. A few of the effects of those differences are highlighted here; see Resources for details.

Bipolar transistors are blazingly fast, but they consume a great deal of power, even in a standby or steady state. Meanwhile, an FET transistor is achingly slow, but consumes no power at all in a steady state. Thus, for applications where long battery life is crucial—and performance isn't—FETs are the way to go. Thus, in the days when computing was still so primitive that people thought that digital watches were a neat idea, it was CMOS chips that powered them. They also powered other applications requiring little power and none-too-fast performance—like housing a personal computer's BIOS. So that's why it's so slow!

Now, another big difference between bipolar and FET transistors is topology: bipolar transistors have a vertical layout, while FET-based chips are built on the horizontal. Thus, there is more room on a FET-based chip. Eventually, around the cusp of the 1980s and 90s, the relentless march of miniaturization approached sizes so small that the larger area of the slower FET-based chips could be filled with enough transistors to whomp the performance superiority of the bipolar model. FET-based chips have one last thing going for them, which is that they interfere electronically with their neighbors much less than bipolar transistors do. So, while bipolar transistors run up against a wall where making them any smaller leads to unacceptable levels of electrical interference, FET-based chips can be made even smaller than that, and so packed even more densely in their larger surface area. Thus, most of the latest advances in nano-scale chip processing have been on CMOS chips.

The other really interesting thing about mainframe chips is their level of redundancy. They are usually packaged together in Multi-Chip Modules (MCM) of 20 or 30 chips or more: fully one half of them are there as backups, ready to take over if an active chip fails. Further, mainframes process each instruction they receive twice, on separate chips, and check their answer before returning it. As we reach the milestone of one billion transistors on a single chip, we may find that kind of stability applied to consumer processors as well.

Custom chips
What do the Nintendo GameCube's Gekko, Cray's X1 supercomputer chips, NVIDIA's latest GeForce processor, and the next-generation Microsoft XBox and Sony PlayStation all have in common? All of them use chip technology licensed from or manufactured by IBM. In the last few years, IBM has begun to open its foundries—and its research—to outside business like never before.

Figure 1. It's wafer-thin: 300mm wafers yield more chips

One of the reasons for that is IBM's new top-of-the-line fab in Fishkill, New York. The Fishkill fab is so up-to-date that it is capable of producing chips with all of the latest acronyms, from copper CMOS technology to Silicon-on-Insulator (SOI) and low-k dielectrics—all on 300mm wafers. And it is so hip that the server room runs exclusively on Linux.

The Fishkill facility, and most of IBM's other fabs, spends a lot of its time producing chips with PowerPC cores. That's because the PowerPC core is really fast and really tiny (leaving lots of room on the chip for customization), and also because the PowerPC architecture is amenable to being coupled with more than one additional coprocessor. This explains its success in highly specialized environments like set-top boxes or the GameCube video game consoles.

IBM foundries are also the world's leading supplier of ASICs (application-specific integrated circuits), from Customizable Control Processor (CCP) options—where a large portion of the design is fixed, but there is plenty of room left for customization—to IBM design expertise in tailoring an existing product to a new application, to support for other suppliers' processors and coprocessors. In short, they're ready for anything.

Fab future
Just twenty years ago, chip components were measured in microns, or thousands of nanometers. Today, chips produced on 300mm wafers contain components with an average size measured in the tens of nanometers. You will of course recall that one nanometer is one millionth of a millimeter, and that a human hair has a thickness of about 100,000 nanometers. At this rate, we will soon be measuring components in Angstroms.

Inexpensive processors with a billion transistors per chip are just around the corner, and industry watchers suggest we will reach speeds of 100 GHz by 2010.

In the meantime, we can look forward to the release of the POWER5 and the Cell super chip, a processor under joint development by Sony, Toshiba, and IBM.

Resources

• IBM's portal for the Power Architecture community is the first step in building a broader community around the Power Architecture. The portal provides a place to gather, find resources, and begin establishing a governance model to help guide future directions for innovation and collaboration.
  
  
• The IBM Power Architecture Pack is a no-charge, downloadable evaluation kit that lets designers create custom Power chips in a simulation environment. It allows engineers to simulate a system-on-chip design based on their own intellectual property coupled with a Power processor.
  
  
• John Cocke's first assignment upon joining IBM in the late 1950s was to work on the Stretch computer. While it never delivered on its promise to outperform the IBM 704 mainframe by a factor of 100, it did outpace its rival by a factor of 30. It also pioneered lookahead, pipelining, branch prediction, multiprogramming, memory protection, generalized interrupts, and the 8-bit byte -- and more! All of these were later used in the IBM System/360 line, and have since trickled out to most chips on the market today.
  
  
• The successor to the 704 was known as Project X, and it competed internally with the successor to Stretch, Project Y. While Project X was to become the IBM S/360 family of mainframe computers, Project Y would become ACS (Advanced Computing Systems), IBM's first attempt at a supercomputer. ACS was the project John worked on after Stretch, and was the forefather of John's next assignment, the 801.
  
  
• A hacker in the true sense of the word, John Cocke changed chip design—and the computing world—forever. For this he received a number of industry and national awards, not the least of which are commendation from The Franklin Institute and the 1987 Turing Award.
  
  
• The S/360 mainframe was released almost exactly 40 years ago, priced to move at a mere $133,000 for a basic configuration. Read a copy of the press release dated April 7, 1964.
  
  
• In the mid 1980s, IBM released the first workstation to use a RISC chip. Named the RT (in keeping with IBM AT and XT machines of the era), it was not destined for greatness. For some interesting technical background on the ROMP processor, read "The IBM RT PC ROMP processor and memory management unit architecture." You'll also find more about the RT and the ROMP chip under RISC in Wikipedia.
  
  
• See also Great Microprocessors of the Past and Present for more on the history of microprocessors; see the IBM Archives and their links page for more on the history of IBM, and see the HISTORY OF COMPUTATION for a one-page history of computing from Babbage to predictions about where we'll be five years from now. Already an expert in computing history? Then take this Pop Quiz.
  
  
• IBM Microelectronics has a great Photo Catalog and a nice group of resources on its technology and innovation page. In particular, you'll want to check out the PowerPC page.
  
  
• In addition to photos of people in bunny suits, IBM Microelectronics also offers Custom chip solutions with the broadest architecture support in the business; from PowerPC cores to Blue Logic cores to other suppliers' cores.
  
  
• IBM Microelectronics also offers Evaluation kits for PowerPC cores, which come with schematics, source code, design details, and a comprehensive selection of tools to enable development of PowerPC-based applications. This page describes what you can expect from a PowerPC processor evaluation kit.
  
  
• Most of IBM Journal of Research and Development Volume 34, Issue 1 is devoted to the original POWER architecture, often referred to in those days also as "the RS/6000 processor" because it powered RS/6000 machines. This issue includes an article on "The evolution of RISC technology at IBM" by John Cocke himself (with Victoria Markstein). (IBM Journal of Research and Development, 1990).
  
  
• You will also find many good reference works on the IBM POWER2 Architecture, the POWER3, and the POWER4 System at the IBM Web site.
  
  
• There is a lot to be said for the revolutionary POWER4. Read also what Extreme Tech thinks of the POWER4 processor.
  
  
• The POWER5 will be in new servers code-named "Squadron," and also in the ASCI Purple supercomputer -- which will boast more than 12,000 POWER5 processors in 197 refrigerator-sized nodes that will cover an area equivalent to the size of two basketball courts -- several orders of magnitude larger than the ENIAC, whose size is the butt of many nerdish jokes. ASCI Purple is expected to be delivered to Lawrence Livermore in the second half of 2004. Servers based on the POWER5 have been up and running at IBM's Poughkeepsie Labs since June 2003.
  
  
• The original Star, or RS64 IV, architecture is described in "A multithreaded PowerPC processor for commercial servers" (IBM Journal of Research and Development, 2000).
  
  
• As Wikipedia, the free encyclopedia, will explain, Bipolar junction transistors (BJT) are not only doped sandwiches, but also something essentially contrary to CMOS. If we could only successfully apply the same advanced processes used in CMOS manufacture today, to bipolar chips, we would make a quantum leap forward to chips with absolutely undreamed-of levels of performance. This CMOS gates demonstration will take your understanding of CMOS to the next level.
  
  
• "Maintaining the benefits of CMOS scaling when scaling bogs down" by E. J. Nowak (IBM Journal of Research and Development, 2002) attempts, among other things, to answer the question What happens when we get to 5 nanometers?, while "The future of CMOS technology" by R.D. Isaac (IBM Journal of Research and Development, 2000) offers great background on challenges facing chip designers, and how and why CMOS have displaced bipolar transistor designs (note especially Table 1!).
  
  
• The immediate future holds the release next year of the Cell "supercomputer on a chip" from the design trio of Sony, Toshiba, and IBM.
  
  
• The developerWorks Linux on POWER developer resources and downloads page is an excellent starting point for software and literature for iSeries, pSeries, and other POWER-based platforms.
  
  
• To get started developing for Linux on POWER, read "EmPOWERing the Linux developer," a guide to the Linux distributions, compilers, and libraries you'll need to write enterprise applications. (developerWorks, March 2004).
  
  
• Find more resources for Linux developers in the DevX Showcase for IBM developerWorks Linux.
  
  
• You'll find a wide selection of books on Linux in the Linux section of the Developer Bookstore.